Adaptive writing method for high-density optical recording apparatus and circuit thereof

ABSTRACT

An adaptive writing method of a high-density optical recording apparatus and a circuit thereof. The circuit includes a discriminator for discriminating a magnitude of a present mark of input NRZI data and magnitudes of leading and/or trailing spaces of the input NRZI data, a generator for controlling the waveform of a write pulse in accordance with the magnitude of the present mark of the input NRZI data and the magnitudes of the leading and/or trailing spaces of the input NRZI data to generate an adaptive write pulse, and a driver for driving a light source by converting the adaptive write pulse into a current signal in accordance with driving power levels for respective channels of the adaptive write pulse. The widths of the first and/or last pulses of the write pulse waveform are varied in accordance with the magnitude of the present mark of input NRZI data and the magnitude of the leading and/or trailing spaces, thereby minimizing jitter to enhance system reliability and performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/774,404,filed Feb. 10, 2004, now U.S. Pat. No. 7,209,423, which is acontinuation of application Ser. No. 09/609,822, filed Jul. 3, 2000, nowU.S. Pat. No. 7,158,461, which is a divisional of application Ser. No.09/359,128, filed Jul. 23, 1999, now U.S. Pat. No. 6,631,110 and claimsthe benefit of Korean Patent Application No. 98-29732, filed Jul. 23,1998, in the Korean Industrial Patent Office, the disclosures of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an adaptive writing method for ahigh-density optical recording apparatus and a circuit thereof, and moreparticularly, to an adaptive writing method for optimizing light powerof a light source, e.g., a laser diode, to be suitable tocharacteristics of a recording apparatus, and a circuit thereof.

2. Description of the Related Art

With the multi-media era requiring high-capacity recording media,optical recording systems employing high-capacity recording media, suchas a magnetic optical disc drive (MODD) or a digital versatile discrandom access memory (DVD-RAM) drive, have been widely used.

As the recoding density increases, such optical recording systemsrequire optimal and high-precision states. In general, with an increasein recording density, temporal fluctuation (to be referred to as jitter,hereinafter) in a data domain increases. Thus, in order to attainhigh-density recording, it is very important to minimize the jitter.

Conventionally, a write pulse is formed as specified in the DVD-RAMformat book shown in FIG. 1B, with respect to input NRZI (Non-Return toZero Inversion) data having marks of 3T, 5T and 11T (T being the channelclock duration), as shown in FIG. 1A. Here, the NRZI data is dividedinto mark and space. The spaces are in an erase power level foroverwriting. The waveform of a write pulse for marks equal to or longerthan 3T mark, that is, 3T, 4T, . . . 11T and 14T is comprised of a firstpulse, a last pulse and a multi-pulse train. Here, only the number ofpulses in the multi-pulse train is varied depending on the magnitude ofa mark.

In other words, the waveform of the write pulse is comprised of acombination of read power (FIG. 1C), peak power or write power (FIG. 1D)and bias power or erase power (FIG. 1E). Here, the respective powersignals shown in FIGS. 1C, 1D and 1E are all low-active signals.

The waveform of the write pulse is the same as that in accordance withthe first generation 2.6 GB DVD-RAM standard. In other words, inaccordance with the 2.6 GB DVD-RAM standard, the waveform of the writepulse is comprised of a first pulse, a multi-pulse train and a lastpulse. Although the rising edge of the first pulse or the falling edgeof the last pulse can be read from a lead-in area to be used, adaptivewriting is not possible since the write pulse is fixed to be constant.

Therefore, when a write operation is performed by forming such a writepulse as shown in FIG. 1B, severe thermal interference may occur backand forth with respect to a mark in accordance with input NRZI data. Inother words, when a mark is long and a space is short or vice versa,jitter is most severe. This is a major cause of lowered systemperformance. Also, this does not make it possible for the system to beapplied to high-density DVD-RAMs, e.g., second generation 4.7 GBDVD-RAMs.

SUMMARY OF THE INVENTION

To solve the above problems, it is an objective of the present inventionto provide an adaptive writing method of a write pulse generated inaccordance with the magnitude of the present mark of input data and themagnitudes of the leading and/or trailing spaces thereof.

It is another objective of the present invention to provide an adaptivewriting circuit for a high-density optical recording apparatus foroptimizing light power of a laser diode by generating an adaptive writepulse in accordance with the magnitude of the present mark of input dataand the magnitudes of the leading and trailing spaces thereof.

Accordingly, to achieve the first objective, there is provided a methodfor writing input data on an optical recording medium by a write pulsewhose waveform is comprised of a first pulse, a last pulse and amulti-pulse train, the adaptive writing method including the steps ofcontrolling the waveform of the write pulse in accordance with themagnitude of the present mark of the input data and the magnitudes ofthe leading and/or trailing spaces to generate an adaptive write pulse,and writing the input data by the adaptive write pulse on the opticalrecording medium.

To achieve the second objective, there is provided an apparatus forwriting input data on an optical recording medium by a write pulse whosewaveform is comprised of a first pulse, a last pulse and a multi-pulsetrain, the adaptive writing circuit including a discriminator fordiscriminating the magnitude of the present mark of the input data andthe magnitudes of the leading and/or trailing spaces, a generator forcontrolling the waveform of the write pulse in accordance with themagnitude of the present mark of the input data and the magnitudes ofthe leading and/or trailing spaces to generate an adaptive write pulse,and a driver for driving the light source by converting the adaptivewrite pulse into a current signal in accordance with driving powerlevels for the respective channels.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objectives and advantages of the present invention will becomemore apparent by describing in detail a preferred embodiment thereofwith reference to the attached drawings in which:

FIGS. 1A through 1E are waveform diagrams of conventional write pulses;

FIG. 2 is a block diagram of an adaptive writing circuit for ahigh-density optical recording apparatus according to an embodiment ofthe present invention;

FIGS. 3A through 3G are waveform diagrams of an adaptive write pulserecorded by the adaptive writing circuit shown in FIG. 2;

FIG. 4 illustrates grouping of input data;

FIG. 5 is a table illustrating the combination of pulses generated bythe grouping shown in FIG. 4;

FIG. 6 is a table illustrating rising edge shift values of a first pulseaccording to the present invention;

FIG. 7 is a table illustrating falling edge shift values of a last pulseaccording to the present invention;

FIG. 8 is a flowchart of an adaptive writing method according to anembodiment of the present invention; and

FIG. 9 is a graph for comparing jitter generated by the adaptive writingmethod of the present invention and the conventional writing method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of an adaptive writing method for ahigh-density optical recording apparatus and a circuit thereof will bedescribed with reference to the accompanying drawings.

An adaptive writing circuit according to the present invention, as shownin FIG. 2, includes a data discriminator 102, a write waveformcontroller 104, a microcomputer 106, a write pulse generator 108 and acurrent driver 110. In other words, the data discriminator 102discriminates input NRZI data. The write waveform controller 104corrects the waveform of a write pulse in accordance with thediscrimination result of the data discriminator 102 and land/groovesignal. The microcomputer 106 initializes the write waveform controller104 or controls the data stored in the write waveform controller 104 tobe updated in accordance with write conditions. The write pulsegenerator 108 generates an adaptive write pulse in accordance with theoutput of the write waveform controller 104. The current driver 110converts the adaptive write pulse generated from the write pulsegenerator 108 into a current signal in accordance with the light powerlevels of the respective channels to drive a light source.

Next, the operation of the apparatus shown in FIG. 2 will be describedwith reference to FIGS. 3 through 7.

In FIG. 2, the data discriminator 102 discriminates the magnitude of amark corresponding to the present write pulse (to be referred to as apresent mark), the magnitude of the front-part space corresponding tothe first pulse of the present mark (to be referred to as a leadingspace, hereinafter) and the magnitude of the rear-part spacecorresponding to the last pulse of the present mark (to be referred toas a trailing space) from input NRZI data, and applies the magnitudes ofthe leading and trailing spaces and the magnitude of the present mark tothe write waveform controller 104.

Here, the magnitudes of the leading and trailing spaces and themagnitude of the present mark may range from 3T to 14T. There can bemore than 1,000 possible combinations. Thus, circuits or memories forobtaining the amounts of shift in rising edges of the first pulses andfalling edges of the last pulses are necessary with respect to allcases, which complicates the system and hardware. Therefore, in thepresent invention, the magnitudes of the present mark and the leadingand trailing spaces of input NRZI data are grouped into a short pulsegroup, a middle pulse group and a long pulse group and the groupedmagnitudes of the present mark and the leading and trailing spaces areused.

The write waveform controller 104 shifts the rising edge of the firstpulse back and forth in accordance with the magnitudes of the leadingspace and the present mark, supplied from the data discriminator 102, orshifts the falling edge of the last pulse back and forth in accordancewith the magnitudes of the present mark and the trailing space, to thusform a write waveform having an optimal light power. Here, themulti-pulse train of a mark takes the same shape as shown in FIG. 3B,that is, 0.5T.

Also, the write waveform controller 104 can correct the rising edge ofthe first pulse of the present mark and the falling edge of the lastpulse of the present mark into different values in accordance withexternally applied land/groove signals (LAND/GROOVE) indicating whetherthe input NRZI data is in a land track or a groove track. This is forforming a write waveform in consideration of different optimal lightpowers depending on the land and groove. A difference of 1-2 mW in theoptimal light powers between the land and the groove, and may bespecifically set or managed by the specifications.

Therefore, the write waveform controller 104 may be constituted by amemory in which data corresponding to a shift value of the rising edgeof the first pulse and a shift value of the falling edge of the lastpulse in accordance with the magnitude of the present mark of input NRZIdata and the magnitudes of the leading and trailing spaces thereof, isstored, or a logic circuit. In the case that the write waveformcontroller 104 is constituted by a memory, the widths of the first pulseand the last pulse are determined as channel clocks (T) plus and minus adata value (shift value) stored in the memory. Also, in this memory,shift values of the first and last pulses of the mark for each of a landand a groove may be stored. A table in which the shift value of therising edge of the first pulse is stored and a table in which the shiftvalue of the falling edge of the last pulse is stored may beincorporated. Alternatively, as shown in FIGS. 6 and 7, two separatetables may be prepared.

A microcomputer 106 initializes the write waveform controller 104 orcontrols the shift values of the first and/or last pulse(s) to beupdated in accordance with recording conditions. In particular, inaccordance with zones, the light power can vary or the shift values ofthe first and last pulses can be reset.

The pulse width data for controlling the waveform of the write pulse isprovided to the write pulse generator 108. The write pulse generator 108generates an adaptive write pulse, as shown in FIG. 3F, in accordancewith the pulse width data for controlling the waveform of the writepulse supplied from the write waveform controller 104 and suppliescontrol signals shown in FIGS. 3C, 3D and 3E, for controlling thecurrent flow for the respective channels (i.e., read, peak and biaschannels) for the adaptive write pulse, to the current driver 110.

The current driver 110 converts the driving level of the light power ofthe respective channels (i.e., read, peak and bias channels) intocurrent for a control time corresponding to the control signal forcontrolling the current flow of the respective channels to allow thecurrent to flow through the laser diode so that an appropriate amount ofheat is applied to the recording medium by continuous ON-OFF operationsof the laser diode or a change in the amounts of light. Here, a recorddomain as shown in FIG. 3G is formed on the recording medium.

FIG. 3A shows input NRZI data, which is divided into mark and space.FIG. 3B shows a basic write waveform, in which the rising edge of thefirst pulse of the write pulse lags behind by 0.5T, compared to therising edge of the present mark. FIG. 3C shows the waveform of a readpower of the adaptive write pulse, FIG. 3D shows the waveform of a peakpower of the adaptive write pulse, and FIG. 3E shows the waveform of abias power of the adaptive write pulse. FIG. 3F shows the waveform ofthe adaptive write pulse proposed in the present invention. The risingedge of the first pulse of the write waveform of the adaptive writepulse may be shifted back and forth in accordance with a combination ofthe magnitude of the leading space and the magnitude of the presentmark. An arbitrary power (Here, a read power or a write power) isapplied during the period corresponding to the shift. Likewise, thefalling edge of the last pulse of the adaptive write pulse may beshifted back and forth in accordance with a combination of the magnitudeof the present mark and the magnitude of the trailing space. Also, anarbitrary power (here, a read power or a write power) is applied duringthe period corresponding to the shift.

Alternatively, the falling edge of the last pulse may be shifted backand forth in accordance with the magnitude of the present mark,regardless of the magnitude of the trailing space of the present mark.Also, rather than shifting the rising edge of the first pulse and thefalling edge of the last pulse, the edge of any one pulse may beshifted. Also, in view of the direction of shift, shifting may beperformed back and forth, only forward or only backward.

FIG. 4 illustrates grouping of input NRZI data, showing two examples ofgrouping. In the first example, if a low grouping pointer is 3 and ahigh grouping pointer is 12, then the mark of a short pulse group is 3T,the marks of a middle pulse group are from 4T to 11T and the mark of along pulse group is 14T. In the second example, if a low groupingpointer is 4 and a high grouping pointer is 11, then the marks of ashort pulse group are 3T and 4T, the marks of a middle pulse group arefrom 5T to 10T and the marks of a long pulse group are 11T and 14T. Asdescribed above, since both the low grouping pointer and the highgrouping pointer are used, utility efficiency is enhanced. Also,grouping can be performed differently for the respective zones.

FIG. 5 illustrates the number of cases depending on combinations ofleading and trailing spaces and present marks, in the case ofclassifying input NRZI data into three groups, as shown in FIG. 4, usinggrouping pointers. FIG. 6 illustrates a table showing shift values ofrising edges of the first pulse depending on the magnitude of theleading space and the magnitude of the present mark. FIG. 7 illustratesa table showing shift values of falling edges of the last pulsedepending on the magnitude of the present mark and the magnitude of thetrailing space.

FIG. 8 is a flow chart illustrating an embodiment of an adaptive writingmethod of the present invention. First, a write mode is set (step S101).If the write mode is set, it is determined whether it is an adaptivewriting mode or not (step S102). If it is determined in step S102 thatthe write mode is an adaptive write mode, a grouping pointer is set(step S103). Then, a grouping table depending on the set groupingpointer is selected (step S104). The selected grouping table may be atable reflecting land/groove as well as the grouping pointer. Also, theselected grouping table may be a table reflecting zones of the recordingmedium.

Shift values of the rising edge of the first pulse are read from thetable shown in FIG. 6 in accordance with a combination of the presentmark and the leading space (step S105), and shift values of the fallingedge of the last pulse are read from the table shown in FIG. 7 inaccordance with a combination of the present mark and the trailing space(step S106).

The adaptive write pulse in which the first pulse and the last pulse arecontrolled in accordance with the read shift value is generated (stepS107). Then, the light powers of the respective channels for thegenerated adaptive write pulse, i.e., read, peak and bias powers, arecontrolled to drive a laser diode (step S108) to then perform a writeoperation on a disc (step S109). If the write mode is not an adaptivewrite mode, a general write pulse is generated in step S107.

FIG. 9 is a graph for comparing jitter generated by the adaptive writingmethod according to the present invention and the conventional writingmethod. It is understood that, assuming that the peak light is 9.5 mW,the bottom power of a multi-pulse train is 1.2 mW, the cooling power is1.2 mW and the bias power is 5.2 mW, there is less jitter generated whenwriting the adaptive write pulse according to the present invention thanwhen generated writing the fixed write pulse according to theconventional writing method. The initialization conditions are a speedof 4.2 m/s, an erase power of 7.2 mW and 100 write operations.

In other words, according to the present invention, in adaptivelyvarying the marks of a write pulse, the rising edge of the first pulseis adaptively shifted in accordance with the magnitude of the leadingspace and the magnitude of the present mark of input NRZI data to thuscontrol the waveform of the write pulse, and/or the falling edge of thelast pulse is adaptively shifted in accordance with the magnitude of thepresent mark and the magnitude of the trailing space of input NRZI datato thus control the waveform of the write pulse, thereby minimizingjitter. Also, the waveform of the write pulse may be optimized inaccordance with land/groove signals. Also, in the present invention,grouping may be performed differently for the respective zones, usinggrouping pointers.

A new adaptive writing method according to the present invention can beadopted to most high-density optical recording apparatuses using anadaptive writing pulse.

As described above, the widths of the first and/or last pulses of awrite pulse waveform are varied in accordance with the magnitude of thepresent mark of input NRZI data and the magnitude of the leading ortrailing space, thereby minimizing jitter to enhance system reliabilityand performance. Also, the width of a write pulse is controlled bygrouping the magnitude of the present mark and the magnitude of theleading or trailing spaces, thereby reducing the size of a hardware.

1. An apparatus for writing input data on an optical recording mediumusing a write pulse waveform including a first pulse, a last pulse and amulti-pulse train, the apparatus comprising: a controller controllingthe write pulse waveform based on a grouping table to generate anadaptive write pulse waveform by varying a position of a rising edge ofthe first pulse of a mark to be written according to a length of themark to be written and a leading space, the grouping table storingrising edge data of the first pulse of the write pulse waveform varyingaccording to corresponding stored values of lengths of marks to bewritten; and an optical pickup optically writing the input data on theoptical recording medium using the adaptive write pulse waveform,wherein the generated adaptive write pulse waveform is generated withoutregard for a trailing space of a present mark being written using theadaptive write pulse waveform, and a width of the first pulse is variedby varying the position of the rising edge.
 2. The apparatus of claim 1,wherein the grouping table stores the rising edge data of the firstpulses for the write pulse waveform according to corresponding storedvalues of lengths of marks to be written and the leading space groupedaccording to a first preset length of the mark and space and a secondpreset length of the mark and space.
 3. The apparatus of claim 2,wherein the grouping table pulse groups comprise a short pulse group andanother pulse group.
 4. The apparatus of claim 1, wherein thecontrolling the write pulse waveform comprises determining from theinput data a length of a present mark to be written, and selecting fromthe grouping table one of the rising edge data of the first pulse of thewrite pulse waveform which is associated with the length of the markwhich corresponds to the determined length.
 5. The apparatus of claim 4,wherein the controlling the write pulse waveform further comprisesdetermining from the input data another length of a space adjacent tothe present mark to be written, and the selecting from the groupingtable comprises selecting one of the rising edge data of the first pulseof the write pulse waveform which is associated with both a length ofthe mark which corresponds to the determined length and a length of aspace which corresponds to the another determined length.
 6. Theapparatus of claim 1, wherein the controlling the write pulse waveformfurther comprises determining from the input data a length of a spaceadjacent to a present mark to be written, and selecting from thegrouping table one of the rising edge data of the first pulse of thewrite pulse waveform which is associated with a length of a space whichcorresponds to the determined length.
 7. An apparatus for writing inputdata on an optical recording medium using a write pulse waveformincluding a first pulse, a last pulse and a multi-pulse train, theapparatus comprising: a controller controlling the write pulse waveformbased on a grouping table having width data grouped in pulse groupswhich group the first and last pulses of the write pulse waveform bycorresponding lengths of a present mark of input data and a leadingspace of the present mark to generate an adaptive write pulse waveformby varying a position of a rising edge of the first pulse of a mark tobe written according to a length of at least a mark to be written and/ora leading space; and an optical pickup optically writing the input dataon the optical recording medium using the adaptive write pulse waveform,wherein the grouping table stores rising edge data of the first pulse ofthe write pulse waveform grouped in corresponding pulse groups accordingto lengths of marks to be written and lengths of spaces adjacent to themarks to be written, and the width of the first pulse is varied byvarying the position of the rising edge.
 8. The apparatus of claim 7,wherein the controlling the write pulse waveform comprises determiningfrom the input data a length of a present mark to be written, andselecting from the grouping table one of the rising edge data of thefirst pulse of the write pulse waveform which is associated with thestored length value of the mark to be written which corresponds to thedetermined length.
 9. The apparatus of claim 8, wherein the controllingthe write pulse waveform comprises determining from the input dataanother length of a leading space adjacent to the present mark, and theselecting from the grouping table comprises selecting one of the risingedge data of the first pulse of the write pulse waveform which isassociated with both a stored length value of a mark which correspondsto the determined length and a stored length value of the space whichcorresponds to the another determined length.
 10. The apparatus of claim7, wherein the controlling the write pulse waveform comprisesdetermining from the input data a length of a lead space of a presentmark to be written, and selecting from the grouping table one of therising edge data of the first pulse of the write pulse waveform which isassociated with a stored length value of the leading space whichcorresponds to the determined length.
 11. The apparatus of claim 7,wherein the generated adaptive write pulse waveform is generatedaccording to the lengths of the present mark and the leading spaceregardless of a length of a trailing space of the present mark.
 12. Theapparatus of claim 7, wherein the pulse groups comprise a short pulsegroup and another pulse group, each member of the another pulse grouphaving lengths greater than each member of the short pulse group.
 13. Anapparatus for writing input data on an optical recording medium using awrite pulse waveform including a first pulse, a last pulse and amulti-pulse train, comprising: a controller controlling the write pulsewaveform based on a grouping table to generate an adaptive write pulsewaveform by varying a position of a rising edge of the first pulse ofthe mark to be written according to a length of at least a mark to bewritten and a leading space, the grouping table storing rising edge dataof the first pulse of the write pulse waveform grouped in correspondingpulse groups according to lengths of marks to be written and lengths ofspaces adjacent to the marks to be written; and an optical pickupoptically writing the input data on the optical recording medium usingthe adaptive write pulse waveform, wherein the width of the first pulseis varied by varying the position of the rising edge.
 14. The apparatusof claim 13, wherein the controlling the write pulse waveform comprisesdetermining from the input data a length of a present mark to bewritten, and selecting from the grouping table one of the rising edgedata of the first pulse of the write pulse waveform which is associatedwith the length of the mark which corresponds to the determined length.15. The apparatus of claim 14, wherein the controlling the write pulsewaveform comprises determining from the input data another length of aspace adjacent to the present mark to be written, and the selecting fromthe grouping table comprises selecting one of the rising edge data ofthe first pulse of the write pulse waveform which is associated withboth a length of a mark which corresponds to the determined length and alength of the space which corresponds to the another determined length.16. The apparatus of claim 13, wherein the controlling the write pulsewaveform comprises determining from the input data a length of a spaceadjacent to a present mark to be written, and selecting from thegrouping table one of the rising edge data of the first pulse of thewrite pulse waveform which is associated with a length of a space whichcorresponds to the determined length.
 17. The apparatus of claim 13,wherein: the present mark comprises another adjacent space other thanthe adjacent space such that the present mark is between the adjacentspace and the another adjacent space; and the generated adaptive writepulse waveform is generated according to the lengths of the present markand the adjacent space regardless of a length of the another adjacentspace of the present mark.
 18. The apparatus of claim 13, wherein thepulse groups comprise a short pulse group and another pulse group, eachmember of the another pulse group having lengths greater than eachmember of the short pulse group.